Screens connected to earth

As a rule, we can state that the screens rigidly connected to earth (solidly bonded connection) almost eliminate induced voltage – the current flowing balances the voltage induced so that the entire screen (assuming zero impedance to ground) potential is ground – but produce significant losses due to induced currents, with a significant reduction of the current rating of the cable.

One way to reduce these losses, is to minimize the separation of the cables putting them at trefoil formation, in contact with each other (symmetrical formation).

On the other hand, the trefoil formation is bad for heat dissipation, since the three single core cables have a warming effect on each other.

In general, the trefoil arrangement with a solidly bonded connection, despite the fact poor heat dissipation, there is an overall increase in transmission capacity due to the reduction of losses due to current flow.